1. Technical Field
The present invention relates to camera modules, and particularly, to a camera modules used in a wide temperature range.
2. Description of Related Art
With the rapid development of electronics technology, camera modules, which typically includes a lens assembly and an image sensor, have been applied in places such as workshops, vehicles, or in electronic devices such as personal computers. In these places or electronic devices, a normal temperature to a work temperature (usually higher than the normal temperature) may be in a wide temperature range. Such camera modules are required to have excellent imaging performance in a wide temperature range.
Actually, the temperature change, i.e. the temperature difference may lead to a change of a focal length of the lens assembly, for example, a focal length at the work temperature may differ from a focal length at a normal temperature. Accordingly, an image plane of the lens assembly may change. The image sensor may not detect an image at the work temperature as clear as an image at the normal temperature. In this way, movement of the lens assembly is needed for compensating the focal length change. However, actuators such as step motors are quite bulky for the above places or electronic devices. In addition, the step motor consumes a substantial amount of power, especially relative to the amount of power that can be stored in a typical battery that powers the camera module.
What is needed, therefore, is a camera module having a simple and energy-efficient mechanism to move the lens assembly when a temperature difference exists.